Stretching and laminating thermoplastic sheet material with other sheet material



Dec. 13, 1949 2,490,946

w. s. cLou STRE ING AND LAMINATING THE OPL IC SHEET TERIAL -TH OTHERSHEET MAT AL ed April 3, 1947 Y HEATING DRUM Fl LM Patented Dec. 13,1949 STRETCHING AND LAMINATING THERMO- PLASTIC SHEET MATERIAL WITH OTHERSHEET MATERIAL William S. Cloud, Wilmette, Ill. Application April 3,1947, Serial No. 739,054 Claims. (Cl. 154-124) In the wrapping ofstandard items, such as v candy bars, which are wrapped by the millions,

very small savings in the cost of wrapping become important.Accordingly, a great deal of effort already has been spent in reducingwrapping costs. Closely associated with this effort to reduce costs hasbeen the effort to obtain a wrapper which will adequately protect thearticles to be wrapped. Candy bars, for example, may become soggy orstale with changes in humidity; if their containers are not hermeticallysealed, they may become infested with insects or contaminated by dirt;other dangers are readily apparent.

Many materials, including those hereinafter set forth, and numerousmethods of utilizing them have been tried over a period of years in thecontinued effort to obtain a wrapper satisfactory both from a cost andfrom a protection viewpoint. None of these appears entirelysatisfactory.

Certain of the materials, such as cellophane, tin, lead and aluminumfoil, and waxed, glassine and other types of paper, are not heatscalable. This precludes this most effective and widely used approach tothe problem of obtaining a hermetically sealed package unless suchmaterials are especially treated with a thermoplastic. Again, certain ofthe materials, such as cellophane and paper, do not provide moistureprotection unless they are specially treated. Some material, such ascellophane present both problems and a solution is combined, a coatingwhich is heat sealable being provided to allow that characteristic andalso to provide moisture protection.

The coatings or lining commonly used are subject to a variety ofobjections. For example, they, and the step of applying them,- arerelatively costly, thus in effect prohibiting the use of severaldesirable materials for given uses. They are frequently not suflicientlyresistant to the penetration of fats and oils, so that an otherwisedesirable material cannot be coated or lined and thus used for givenpurposes. Certain admixtures of microcrystalline or amorphous waxes withsynthetic resins may possess every desirable quality needed for the bodyof a container which is designed to hold grease or shortening, butat'the same time such mixture may not be suitable for a coating on amaterial designed for candy. and other food wrappers, because thematerial itself is inherently tacky, or because it has qualities whichprevent it from being handled readily in automatic machinery.

- Certain other materials sometimes used in packaging are too costly topermit wide use, or are subject to other objections. Foil is expensiveand is relatively difficult to handle on a production line. The rubberhydrochloride sheet material sold by the Goodyear Tire & Rubber Company,of Akron, vOhio, under the trade name Pliofilm" has good generalcharacteristics in moisture protection and ease of sealing, but itscost, especially when it is printed, is high.

Known methods of laminating sheet materials have not provided a solutionof these problems. For example, the lamination of sheets of Pliofilm,which had been stretched lengthwise to make it go further and thusreduce its cost, to sheets of paper has been proposed. This wouldproduce a laminated sheet or web the paper side of which could easily beprinted and the Pliofilmside of which would be heat-scalable andresistant to acids and oils. These laminated sheets would be flexible,sanitary and provide moisture protection. However, difficulties inhandling the sheets, waste incurred in trimming the edges thereof andother anticipated factors, so raised the necessary price that widedemand has not been forthcoming for these sheets. These sheets wouldalso be subject to the limitations of Pliofilm which has been stretchedin only one direction. Such a stretch is relatively uneven and thereforethe sheet will tear or break if the stretching operation is continuedlong enough. This tearing or breaking may occur before the sheet isreduced to the desired thinness and, if not, an undesirable variation inthickness will result. This one directional stretch rearranges themolecules in the Pliofilm so that it can be torn far easier in thedirection of the stretch than it can be in a direction perpendicularthereto, so that a sheet of varying strength results.

I have invented or discovered a novel method whereby a sheet of organicplastic material, such as Pliofilm, may be stretched in two directionswhile so controlled that approximately uniform thickness and strengthresult, thus allowing an unusual amount of stretching, and may be lami-4 nated to another sheet, of paper, foil, or whatever material isdesired. The result of this stretching in two directions is that themolecules of elongate shape are disposed mainly parallel to the surfaceof the sheet and within this plane are either distributed promiscouslyor predominantly disposed at rightangles to each other, thus resultingin resistance to tear in more than one direction.

The novel method produces a wrapping material which combines low costwith adequate pro- 3 tection for the articles to be wrapped. It may beutilized on standard wrapping machinery.

Other objects and advantages of my invention will be apparent from thefollowing description and from the drawing, in which:

Fig. 1 is a diagrammatic view of one form of apparatus chosen forillustration of my invention, shown in side elevation, some detailsbeing omitted for clarity. A

Although the law requires a full and exact description of at least oneform of the invention, such as that which follows, it is, of course, thepurpose of a patent to cover each new inventive concept therein nomatter how it may later be disguised by variations in form or additionsof further improvements; and the appended claims are intended toaccomplish this purpose by particularly pointing out the parts,improvements, or combinations in which the inventive concepts are found.

In order to illustrate how my method of stretching and laminatingthermoplastic sheet material with other sheet material is performed,attention is directed to Figure 1, wherein a web I of unprinted,stretchable sheet material is fed or unwound from roll 2.

Certain of the web materials which will be used in connection with myinvention are normally non-stretchable at room temperature. Some. suchas Pliofilm, must be heated to render them soft and stretchable. Theterm stretchable" is, of course, relative since any film will stretchminutely. In Figure l, I have illustrated heating of the web material byhaving idler rolls 3 and 3' guide it around heated drum 4. However, itis to be understood both that this is not the only method of heating theweb material and that, in the case of a web material which must bechemically treated to render it stretchable, this heating would beomitted and the appropriate chemical treatment substituted. I thenstretch the web progressively.

In Figure l, I have illustrated an apparatus for progressivelystretching successive portions of the web both laterally andlongitudinally and for holding the stretched web against contraction.Such apparatus is especially desirable for use in connection with webmaterial such as Pliofilm which, when heated and stretched, becomes veryelastic.

From roll 3, the web is guided by idler roll 5 to a position where itsedges are gripped at spaced intervals by holding means on the tips ofarms 8, pivotally mounted on sprocket chains 1. Arms 6 are constructedand operate in substantially the same manner as arms l0 described in mycopending application, Serial No. 692,323, filed August 22, 1946,wherein substantially similar stretching apparatus is fully described,said description being incorporated herein by reference. For the purposeof this application it is sufficient to indicate that sprocket chains Imay be driven at the same rate as is web I. Mounted on chains I at fixedintervals are arms 6, the tips of which bear holding means. These armsare pivotally mounted so that, from the position extending horizontallyinwardly toward each other at which they grip web I, they may be forcedby guide bars 8 to a vertical position, to force the opposed rows of theweb-holding tips away from each other and thereby stretch the weblaterally. Upon completion of the lateral stretch of web I, theweb-holding tips arrive at the top of the sprocket Ill. As they arecarried from this position around the sprocket, the distance between theweb-holding tips of arms 8, in each of the rows carried on chains I, isincreased longitudinally, thereby stretching web I lengthwise.

It is to be understood that web I may be stretched by other means thanthose which I have illustrated. For example, it may be stretchedlengthwise by driving idler roll 3' and all subsequently operating partsof the apparatus at a faster rate than heating drum 4; or it may bestretched laterally by the use of tentering means after it has beenrendered stretchable, in which case provision would have to be made forholding it against contraction until after the lamination; or acombination of these may be used.

In timed relationship with the movement of web I, a second web l l ofpaper. foil, or whatever other suitable material is desired to belaminated with web 1, is feed or unwound from roll II. If this materialis one to which web 1 will not seal under pressure, it may be guided byidler rolls i3 into a position where a suitable binder, such as glue, isapplied to it.

The two webs i and Ii are brought together and passed between pressurerolls I4 and W to laminate them.

Web H is preferably narrower than stretched web I, to an extentsufficient to allow it to avoid contacting the web-holding tips of arms6 and to be laminated to web i across the complete width of web ll. Thisis ensured by the disclosed apparatus wherein the web-holding tips ofarms 6 extend beyond the sides of pressure roll H. The portion of web Iwhich is to be laminated is preferably guided to pressure roll H byguide roll 9, which may be driven by any desired means.

As the two webs are being laminated, the excess edge of web I passesbetween cutting rolls l6 and drum I4 which trims off the unlaminatededges of web I, this excess being carried away by the web-holding tips.When web I is Plioillm, I prefer to substitute hot wires for cuttingrolls l6. At this time the laminated web can also be divided into stripsof any desired width by passing it between suitably placed cuttingrolls.

As web I of the laminated web is in a stretched condition, and may be inan elastic condition, depending on the material used, Pliofilm, forexample, being elastic when heated and stretched, it may be necessary tohold the laminated web to avoid its being distorted by the shrinking orcontracting of web I. This may be done by winding it on pressure roll Hwhich may be flexibly mounted to allow this dual use. The laminated webmay be left on roll l4 until web I has set so as to lose its elasticquality. When web I is made of certain materials it may be set by othermeans, as by blowing cool air on it, so that it may not be necessary toroll up the laminated web and allow it to set.

It is to be noted that the difliculty and expense of slip-sheeting,heretofore necessary when winding or rolling up certain softened andstretched materials, such as Pliofilm, because of the tendency of suchmaterials to adhere to whatever they contact, is eliminated, web ll ofthe laminated web serving as a "slip sheet.

I claim:

1. Web treating apparatus including spaced rows of traveling holdingmeans having web engaging portions for holding the longitudinal edges ofthe web at spaced points, means for progressively feeding the web tosaid holding means in generally outstretched condition, and means forprogressively separating the rows laterally and progressivelylongitudinally separating from one another the web engaging portions ofeach row while the webis held thereby, to stretchthe web, and means forapplying to said stretched web a second web and rolling up the websjointly, while the stretched web is thus held stretched, to maintain itagainst contraction until it sets.

2. Web treating apparatus including spaced rows of traveling holdingmeans having web engaging portions for holding the longitudinal edges ofthe web at spaced points, means for progressively feeding the web tosaid holding means in generally outstretched condition, and means forprogressively separating the rows laterally and progressivelylongitudinally separating from one another the web engaging portions ofeach row while the web is held thereby, to stretch the web, means forapplying to said stretched web a second web and rolling up the websjointly, while the stretched web is thus held stretched, to maintain itagainst contraction until it sets, and means to apply a binder to one ofsaid webs before they are brought together.

3. Web treating apparatus including spaced rows of traveling holdingmeans having web engaging portions for, holding the longitudinal edgesof the web at spaced points, means for progressively feeding the web tosaid holding means in generally outstretched condition, and means forprogressively separating the rows laterally and progressivelylongitudinally separating from one another the web engaging portions ofeach row while the web is held thereby, to stretch the web, and meansfor applying to said stretched web a second web and rolling up the websjointly, while the stretched web is thus held stretched, to maintain itagainst contraction until it'set's, and means effective as the webs arerolled up for trimming from said stretched web the edges engaged by theholding means, said holding means at the time of rolling up lying beyondthe ends of the roll.

4. The method of treating a web of plastic material which comprisescontinuously advancing a web of said material, progressively holding theweb at spaced points along the longitudinal edges thereof, progressivelymoving the opposed points laterally away from one another to stretch theweb transversely, and progressively longitudinally stretching theportion of the web between said points while said portions of the webare being held against lateral contraction, applying a second web to thestretched web and rolling up said webs jointly, while the stretched webis held stretched in both directions, to maintain the stretched webagainst contraction until it has set.

5. The method of treating a web of rubber hydrochloride which comprisescontinuously advancing a web of said material, progressively holding theweb at spaced points along the longitudinal edges thereof, progressivelymoving the opposed points laterally away from one another to stretch theweb transversely, and progressively longitudinally stretching theportion of the web between said points while said portions of the webare being held against lateral contraction, applying a narrower secondweb to the stretched web and rolling up said webs jointly, while thestretched web is held stretched in both directions, to maintain thestretched web against contraction until it has set.

6. The method of treating a web of rubber hydrochloride which comprisescontinuously advancing a web of said material, progressively heating theweb to facilitate the stretching thereof,

progressively holding the web at spaced points. along the longitudinaledges thereof, progressively moving the opposed points laterally awayfrom one another to stretch the web transversely, and progressivelylongitudinally stretching the portion of the web between said pointswhile said portions of .theweb are being held against lateralcontraction, applying a second web to the stretched web and rolling upsaid webs jointly, while the stretched web is held stretched in bothdirections, to maintain the stretched web against contraction until ithas set.

7. The method of treating a web of plastic material which comprisescontinuously advancing a web of said material, progressively holding theweb at spaced points along the longitudinal edges thereof, progressivelymoving the opposed points laterally away from one another to stretch theweb transversely, and progressively longitudinally stretching theportion of the web between said points while said portions of the webare bein held against lateral contraction, applying a narrower web tothe stretched web and rolling up said webs jointly, while the stretchedweb is held stretched in both directions, to maintain the stretched webagainst contraction until it has set, and trimming the stretched web tothe width of the narrower web as they are rolled up.

8. The method of treating a web of rubber hydrochloride which comprisesadvancing a web of said material, heating the web to facilitatestretching it, progressively holding the web along the longitudinaledges thereof, progressively moving the longitudinal edges laterallyaway from one another to stretch the web transversely, and progressivelylongitudinally stretching the web between points held along the edgeswhile said portions of the web are being held at said points againstlateral contraction, applying a second web to the stretched web androlling up said webs jointly, while the stretched web is held stretchedin both directions, to maintain the stretched web against contractionuntil it has set.

9. The method of treating a web of rubber hydrochloride which comprisesadvancing a web of said material, heating the web to facilitatestretching it, progressively holding the web alon the longitudinal edgesthereof, progressively moving the longitudinal edges laterally away fromone another to stretch the web transversely, and progressivelylongitudinally stretching the web, applying a second web to thestretched web and rolling up said webs jointly, while the stretched webis held stretched in both directions by holding the stretched web alongits longitudinal edges adjacent the point at which the stretched web andsaid second web meet and are rolled together, to maintain the stretchedweb against contraction until it has set.

10. Laminating apparatus including means for moving and softening a webof rubber hydrochloride, comprising a driven heated drum, opposed rowsof gripping elements adapted to grip opposite edges of said web as it ispassed from said drum, such elements being carried on arms pivotallymounted at spaced intervals on sprocket chains, guide bars adapted toswing the arms to increase the lateral distance betweenoppositelydisposed gripping elements as they travel to stretch said weblaterally, sprockets over which said sprocket chains pass with the saidarms generally in a plane perpendicular to the axis of said sprockets toswing said arms on each of said chains apart angularly to separate saidgripping elements, to stretch said web longitudinally,

means for moving a web of paper comprising a driven drum, a rollerrotating in contact'with severing the strips of said first web beingheld by 8 said gripping elements from the balance or said web as it isbeing laminated with said second web.

WILLIAM S. CLOUD.

mm ENCES cnm The following references are of record in the iile of thispatent:

UNITED STATES PATENTS 10 Number Name Date 1,211,706 Hoerbelt Jan. 9.1917 2,201,416 Wagner May 21, 1940 $439,177 Young Oct. 14, 1947

